Generally, when a vehicle is running, a combustion noise is generated in an engine compartment of the vehicle and flows into an interior of the vehicle.
Such a combustion noise may be generated and propagate into the interior of the vehicle in various magnitudes depending on opening angles of engine valves associated with an engine rotational speed and an accelerator pedal effort, the number of passengers, or various temperature conditions of the interior of the vehicle.
The combustion noise is generated as a low frequency combustion noise or a high frequency combustion noise depending on a driving condition of the vehicle. The low frequency combustion noise may be reduced by calculating a phase of the low frequency combustion noise and then outputting a reverse-phase sound through a speaker installed in the interior of the vehicle.
However, it is difficult to effectively reduce a high frequency combustion noise generated in the vehicle. Accordingly, when the vehicle is running, a driver may feel a sense of fatigue due to the high frequency combustion noise.
The above information disclosed in this Background section is only to enhance the understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.